A universal joint provides a means to couple two rotating shafts to one another in an end to end relationship despite the shafts not necessarily being in line with one another. In reference to automobiles, a pair of universal joints are often used to couple a rotating drive shaft at a first end to the output of a transmission or transfer case and at a second end to the input of a differential, which in turn drives the rear and or front wheels of the automobile. In front or four-wheel drive cars, universal joints are often employed to allow articulation between a pair of front axles extending in opposite directions from a front differential or transmission and a pair of stub axles carrying the wheels, thus permitting the front wheels to pivot to permit steerage.
Referring to FIG. 1, a previously developed universal joint 10 is depicted. The universal joint 10 is comprised of a main body, referred to as a cross or a spider 12, having four co-planar trunnions 14 extending radially outward from the spider 12 at 90 degree intervals. Journals 16 are formed on the distal ends of the trunnions 14 to accept bearing cups 18 thereupon. Disposed between the bearing cups 18 and the  journals 16 are a plurality of needle roller bearings 20 used to reduce friction as the trunnions 14 rotate within the bearing cups 18.
During installation, a first pair of collinear trunnions 14A and 14B are inserted within a pair of opposing bosses 22 of a first yoke 24 of a first drive shaft 26. A pair of bearing cups 18 and needle roller bearings 20 are then inserted into the bosses 22 so as to be received upon the journals 16 of the trunnions 14A and 14B. The bearing cups 18 are secured with retaining rings 34, as is well known in the art. A second pair of collinear trunnions 14C and 14D (not shown) are then inserted within a pair of opposing bosses 28 of a second yoke 30 of a second drive shaft 32. A second pair of bearing cups 18 and needle roller bearings 20 are then inserted into the bosses 28 so as to be received upon the journals 16 of the trunnions 14C and 14D (not shown). The bearing cups 18 are secured with retaining rings 34, as is well known in the art. Once the universal joint 10 is installed, the first drive shaft 26 may rotate with two degrees of freedom relative to the second drive shaft 32, each degree of freedom defined by one of the collinear pairs of trunnions 14A and 14B or 14C and 14D. Thus, the first drive shaft 26 may rotate at an angle relative to the second drive shaft 32 during rotation of the shafts 26 and 32 without binding.
Still referring to FIG. 1, although previously developed universal joints are effective at transferring loads between two non-aligned shafts, they are not without their limitations and problems. Although previously developed universal joints 10 are adequate for use in low load conditions, they tend to break down when subjected to high loads imposed during severe usage situations. One reason lies in the use of needle roller bearings 20. The needle roller bearings 20 of previously developed universal joints tend to concentrate the forces exerted between the journals 16 of the universal joint 10 and the bearing cups 18 along finite pressure lines. More specifically, the forces exerted between the journals 16 and the bearing cups 18 are concentrated along a first contact line formed between the inner surface of the bearing cups 18 as they engage the outer surfaces of the roller needle bearings 20, and a second contact line formed by the outer surfaces of the journals 16 as they engage the roller needle bearings 20. Thus, during high loads, the concentration of large forces upon the minimal contact area represented by the contact lines often causes premature failure of the universal joint 10. 
Further, the grease delivery systems of previously developed universal joints are inadequate to supply grease at sufficiently high pressures to maintain the bearing cups in an adequate state of lubrication when subjected to high loads. Moreover, existing universal joints 10 depend on centrifugal forces to supply grease to the bearing cups. The pressure created through centrifugal forces may be insufficient to adequately pressurize the grease for high load conditions. This is especially true for universal joints 10 exhibited to high loads and low revolution (i.e. low RPM) conditions. Further still, the manner of installation of existing universal joints limits the size of the spider that may be used, thus limiting the strength of the universal joint, thereby increasing the potential of failure of the universal joint. Further yet, under high torque conditions, previously developed trunnions tend to dig into the needle roller bearings as the bearing cups cant and/or deform under the load.